Added entropy pool

core/src/main/java/org/bouncycastle/crypto/prng/SP800SecureRandom.java

@@ -67,4 +67,14 @@ public byte[] generateSeed(int numBytes)
     {
         return EntropyUtil.generateSeed(entropySource, numBytes);
     }
+
+    /**
+     * Force a reseed of the DRBG
+     *
+     * @param additionalInput optional additional input
+     */
+    public void reseed(byte[] additionalInput)
+    {
+        drbg.reseed(additionalInput);
+    }
 }

prov/src/main/java/org/bouncycastle/jcajce/provider/drbg/DRBG.java

@@ -5,10 +5,15 @@
 import java.security.Provider;
 import java.security.SecureRandom;
 import java.security.SecureRandomSpi;
+import java.util.concurrent.atomic.AtomicBoolean;
+import java.util.concurrent.atomic.AtomicInteger;
+import java.util.concurrent.atomic.AtomicReference;
 
 import org.bouncycastle.crypto.digests.SHA512Digest;
+import org.bouncycastle.crypto.macs.HMac;
 import org.bouncycastle.crypto.prng.EntropySource;
 import org.bouncycastle.crypto.prng.EntropySourceProvider;
+import org.bouncycastle.crypto.prng.SP800SecureRandom;
 import org.bouncycastle.crypto.prng.SP800SecureRandomBuilder;
 import org.bouncycastle.jcajce.provider.config.ConfigurableProvider;
 import org.bouncycastle.jcajce.provider.util.AsymmetricAlgorithmProvider;
@@ -108,15 +113,22 @@ private static SecureRandom createBaseRandom(boolean isPredictionResistant)
 
             EntropySource initSource = entropyProvider.get(16 * 8);
 
+            byte[] personalisationString = isPredictionResistant ? generateDefaultPersonalizationString(initSource.getEntropy())
+                                                                 : generateNonceIVPersonalizationString(initSource.getEntropy());
+
             return new SP800SecureRandomBuilder(entropyProvider)
-                                .setPersonalizationString(generateDefaultPersonalizationString(initSource.getEntropy()))
+                                .setPersonalizationString(personalisationString)
                                 .buildHash(new SHA512Digest(), Arrays.concatenate(initSource.getEntropy(), initSource.getEntropy()), isPredictionResistant);
         }
         else
         {
-            SecureRandom randomSource = createInitialEntropySource();   // needs to be done late, can't use static
+            SecureRandom randomSource = new HybridSecureRandom();   // needs to be done late, can't use static
+
+            byte[] personalisationString = isPredictionResistant ? generateDefaultPersonalizationString(randomSource.generateSeed(16))
+                                                                 : generateNonceIVPersonalizationString(randomSource.generateSeed(16));
+
             return new SP800SecureRandomBuilder(randomSource, true)
-                .setPersonalizationString(generateDefaultPersonalizationString(randomSource.generateSeed(16)))
+                .setPersonalizationString(personalisationString)
                 .buildHash(new SHA512Digest(), randomSource.generateSeed(32), isPredictionResistant);
         }
     }
@@ -196,4 +208,106 @@ private static byte[] generateNonceIVPersonalizationString(byte[] seed)
         return Arrays.concatenate(Strings.toByteArray("Nonce"), seed,
             Pack.longToLittleEndian(Thread.currentThread().getId()), Pack.longToLittleEndian(System.currentTimeMillis()));
     }
+
+    private static class HybridSecureRandom
+        extends SecureRandom
+    {
+        private final AtomicBoolean seedAvailable = new AtomicBoolean(false);
+        private final AtomicInteger samples = new AtomicInteger(0);
+        private final SecureRandom baseRandom = createInitialEntropySource();
+        private final SP800SecureRandom drbg;
+
+        HybridSecureRandom()
+        {
+            drbg = new SP800SecureRandomBuilder(new EntropySourceProvider()
+                {
+                    public EntropySource get(final int bitsRequired)
+                    {
+                        return new SignallingEntropySource(bitsRequired);
+                    }
+                })
+                .setPersonalizationString(Strings.toByteArray("Bouncy Castle Hybrid Entropy Source"))
+                .buildHMAC(new HMac(new SHA512Digest()), baseRandom.generateSeed(32), false);     // 32 byte nonce
+        }
+
+        public byte[] generateSeed(int numBytes)
+        {
+            byte[] data = new byte[numBytes];
+
+            // after 20 samples we'll start to check if there is new seed material.
+            if (samples.getAndIncrement() > 20)
+            {
+                if (seedAvailable.getAndSet(false))
+                {
+                    samples.set(0);
+                    drbg.reseed(null);
+                }
+            }
+
+            drbg.nextBytes(data);
+
+            return data;
+        }
+
+        private class SignallingEntropySource
+            implements EntropySource
+        {
+            private final int byteLength;
+            private final AtomicReference entropy = new AtomicReference();
+            private final AtomicBoolean scheduled = new AtomicBoolean(false);
+
+            SignallingEntropySource(int bitsRequired)
+            {
+                this.byteLength = (bitsRequired + 7) / 8;
+            }
+
+            public boolean isPredictionResistant()
+            {
+                return true;
+            }
+
+            public byte[] getEntropy()
+            {
+                byte[] seed = (byte[])entropy.getAndSet(null);
+
+                if (seed == null || seed.length != byteLength)
+                {
+                    seed = baseRandom.generateSeed(byteLength);
+                }
+                else
+                {
+                    scheduled.set(false);
+                }
+
+                if (!scheduled.getAndSet(true))
+                {
+                    new Thread(new EntropyGatherer(byteLength)).start();
+                }
+
+                return seed;
+            }
+
+            public int entropySize()
+            {
+                return byteLength * 8;
+            }
+
+            private class EntropyGatherer
+                implements Runnable
+            {
+                private final int numBytes;
+
+                EntropyGatherer(int numBytes)
+                {
+                    this.numBytes = numBytes;
+                }
+
+                public void run()
+                {
+                    entropy.set(baseRandom.generateSeed(numBytes));
+                    seedAvailable.set(true);
+                }
+            }
+        }
+    }
 }